Fish Catcher vs built-in Safe Browsing
Fish Catcher is a free, open-source add-on that gives local, plain-language phishing warnings; built-in Safe Browsing is the cloud list already inside Chrome and Firefox that warns or blocks known dangerous sites.
A layer you add versus a layer already there
Google Safe Browsing is built into most major browsers and generally runs by default. It checks the sites you visit against a cloud list of known dangerous pages and steps in with a full-page warning or block when there is a match. It is well maintained, widely trusted, and requires no setup because it is already on. The trade-off is that it works from a list of sites that are already known to be bad, and its checks involve the browser's cloud service rather than staying entirely on your device.
Fish Catcher is something you choose to add. Its default checks run in your browser, nothing about the page leaves the device by default, and there is no account. Instead of relying on a page already being on a known-bad list, it reads the page and link in front of you and reasons about them, then shows a risk color and a plain-language reason. It warns rather than blocks. The two approaches are complementary: one catches sites already known to be dangerous, the other looks for the signs of a scam before a site is widely listed.
Different kinds of coverage
Safe Browsing's strength is a large, continuously updated cloud list maintained by Google and used across browsers. For sites that are already reported and confirmed dangerous, it is fast and broad, and it will often block them outright. Its focus is that known-bad list rather than per-page heuristic analysis of a site you have never visited.
Fish Catcher aims at the gap before a site lands on such a list. It flags lookalike domains and homoglyphs, URL tricks, and fake login forms, and it uses a bundled blocklist plus a daily community feed from Phishing.Database, URLhaus, and OpenPhish. It adds an on-device model for machine-generated domains, checks for adversary-in-the-middle and device-code scams, ships scam packs for wallet-phrase and fake tech-support pages, and includes a download guard. Across 100,000 Majestic Million domains its measured false-positive rate was 0.005%, reproducible with a script in the project. You can also enable Safe Browsing inside Fish Catcher as an optional extra layer, using your own key.
| Aspect | Fish Catcher | Built-in Safe Browsing |
|---|---|---|
| Privacy model | Local-first; nothing about the page leaves the browser by default; no account, no tracking | Cloud list and lookup run by the browser vendor; some data is typically involved in checks |
| Open source | Yes, MIT licensed | Proprietary service built into the browser |
| Blocks vs warns | Warns, never blocks; you decide | Typically warns and blocks known dangerous sites |
| Detection approach | On-device heuristics and model, bundled and daily blocklists, plus optional Safe Browsing | Cloud list of known-dangerous sites, matched as you browse |
| Cost | Free | Free and already included |
| Best for | Catching scam signals before a site is widely listed, with clear reasons | Broad, low-effort coverage of sites already known to be dangerous |
Who should pick which
This is less an either-or than the other comparisons. Safe Browsing is already protecting most people and there is little reason to turn it off. Fish Catcher is worth adding if you want warnings that reason about a page rather than only checking a known-bad list, if you want to see the specific reason a page looks risky, and if you prefer that your default checks stay on your device. Running both gives you a known-bad list plus a heuristic layer that can catch newer or more targeted scams.
Where Fish Catcher is weaker
Fish Catcher is new and less battle-tested than Safe Browsing, which has years of scale behind it. Its bundled and feed blocklist is much smaller than the cloud list Safe Browsing draws on, so for sites that are already confirmed dangerous, Safe Browsing will often have wider and faster coverage. Fish Catcher warns rather than blocks, so it will not stop you the way a full-page block does. And by default it does not use a cloud reputation service, though you can add Safe Browsing as an opt-in layer.
Common questions
If my browser already has Safe Browsing, do I need Fish Catcher?
You do not need it, but it covers a different gap. Safe Browsing is strongest on sites already known to be dangerous. Fish Catcher looks for scam signals on pages that may not be listed yet, and it explains why a page looks risky. Many people run both.
Should I turn off Safe Browsing if I install Fish Catcher?
No. Leave Safe Browsing on. The two are designed to complement each other, and keeping both means you get a broad known-bad list plus an on-device heuristic layer. Fish Catcher warns rather than blocks, so it does not replace the block behavior Safe Browsing provides.